The present invention pertains to a respirator with a breathing circuit between the gas delivery element and the patient connection piece and a process for operating a respirator.
Respirators with a breathing circuit are used either in the area of intensive respiration performed over long periods of time or as anesthesia apparatuses with corresponding metering means for metering anesthetics into the breathing circuit in order to guarantee a possibly controlled release to the patient being respirated, e.g., before and during an operation.
A respirator with a breathing circuit with a gas delivery element is described in DE 34 22 066 C2. However, there is no possibility with the disclosed system to ensure a defined gas volume flow to the patient during the phases of inspiration and to make possible the monitoring of the current operating state.
The primary object of the present invention is to provide a respirator with a breathing circuit and a corresponding process for operating the respirator, with which defined breathing gas volumes are delivered to the patient despite a strong breathing gas volume flow guided in the breathing circuit and the current operating state can be reliably monitored.
According to the invention, a respirator with a breathing circuit is provided with a gas delivery element designed as a rotary compressor connected on an inlet side to a reversible breathing gas reservoir and on the outlet side to a patient connection piece for inspiration via a first gas volume flow sensor with a first nonreturn valve. A second gas volume flow sensor is located in the connection line between the patient connection piece and the patient being respirated. A patient connection is connected for expiration to a second nonreturn valve via a third gas volume flow sensor and to a reversible breathing gas reservoir via a controllable shut-off valve. At least one measuring and control unit is connected to the gas volume flow sensors. The control unit receives their measured signals and sends control signals to the gas delivery element and to the controllable shut-off valve.
According to another aspect of the invention, a process for operating a respirator is provided wherein the beginning of each phase of inspiration and/or expiration is triggered either in a time-controlled manner or by a measured signal brought about by inspiration or expiration at the second gas volume flow sensor. In one mode of operation during each phase of inspiration, the controllable shut-off valve is closed, the gas delivery element is activated, so that it delivers breathing gas from the reversible breathing gas reservoir, and the speed of rotation of the gas delivery element is controlled as a function of the measured signals of the first gas volume flow sensor. During each phase of expiration, the speed of rotation of the gas delivery element is reduced to a lower value or to zero, the controllable shut-off valve is opened, and the exhaled gas volume flow is measured by means of a second gas volume flow sensor, and the speed of rotation of the gas delivery element is controlled as a function of the measured signals of the first gas volume flow sensor. During the switching phases of the controllable shut-off valve, the gas volume flow to the patient is determined from the difference of the measured signals of the first and third gas volume flow sensors at the beginning and at the end of each phase of inspiration, and the speed of rotation of the gas delivery element is controlled as a function of this difference.
One essential advantage of the present invention is the use of a gas delivery element, which is designed as a rotary compressor, especially a radial compressor, which can have a highly compact design and can be controlled very rapidly due to its dynamic properties by setting the speed of rotation. To obtain the most homogeneous breathing gas concentration possible in the breathing circuit, the breathing gas is circulated through the gas delivery element with a high speed of rotation and high delivery capacity before each phase of inspiration, i.e., a so-called rinsing gas volume flow of a time average of, e.g., 30 L per minute is generated.
During each phase of inspiration, according to one mode of operation, the expiratory branch of the breathing circuit is completely closed by means of a controllable shut-off valve, so that no expiratory gas volume flow is present in the expiratory branch and no rinsing gas volume flow guided in the breathing circuit is present. The inspiratory gas volume flow in the inspiratory branch of the breathing circuit is measured by means of a first gas volume flow sensor and it directly corresponds to the gas volume flow to the patient. The respirator is controlled by means of one central measuring and control unit or a plurality of measuring and control units as a function of this measured gas volume flow to the patient, so that a defined patient volume can be metered in a time-dependent manner. The gas volume flow measurement is performed during this phase only via the first gas volume flow sensor, so that the accuracy of the measurement depends directly on the accuracy of the first gas volume flow sensor itself.
The expiratory branch of the breathing circuit is opened by means of the controllable shut-off valve during each phase of expiration after the speed of rotation of the gas delivery element has first been reduced to a lower value or even to zero and the patient is breathing out.
In addition to the gas volume flow exhaled by the patient, a rinsing gas volume flow is metered by means of the gas delivery element by increasing the speed of rotation of the gas delivery element, the amount of the rinsing gas volume flow being such that extensive homogenization of the breathing gas concentration is achieved in the breathing circuit, on the average, in the course of one breath. Since the exhaled gas volume flow and the rinsing gas volume flow are superimposed to one another in the expiratory branch of the breathing circuit, the exhaled gas volume flow is determined directly by means of a second gas volume flow sensor in the connection line between the patient connection piece and the patient being respirated. Finally, the inspiratory gas volume flow to the patient, in one mode of operation, is determined during the switching phases of the controllable shut-off valve at the beginning and at the end of each phase of inspiration from the difference of the measured signals of the first and third gas volume flow sensors arranged in the inspiratory branch and in the expiratory branch of the breathing circuit, because the difference of these measured signals is also relatively small at high rinsing gas volume flows and is subject to high inaccuracies. The speed of rotation of the gas delivery element is controlled during these switching phases as a function of this difference of the measured signals.
Another mode of operation of the respirator includes triggering the beginning of each phase of inspiration and/or expiration either in a time-controlled manner or by a measured signal brought about by inspiration or expiration at the second gas volume flow sensor. The controllable shut-off valve is controlled during each phase of inspiration with the third gas volume flow sensor such that a gas volume flow is maintained in the respirator and the speed of rotation of the gas delivery element is only controlled as a function of the pressure detected in the respirator. The speed of rotation of the gas delivery element is reduced during each phase of expiration to a lower value or to zero. The controllable shut-off valve is opened, and the exhaled gas volume flow is measured with the second gas volume flow sensor. The speed of rotation of the gas delivery element is controlled during expiration as a function of measured signals of the first gas volume flow sensor.
The further process feature of switching between the first mode and the second mode provides advantages including a more versatile system.
One exemplary embodiment of the present invention will be explained in greater detail below on the basis of the only figure, which schematically shows the arrangement of a respirator according to the present invention, adapted to the requirements in the area of anesthesia.
The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this disclosure. For a better understanding of the invention, its operating advantages and specific objects attained by its uses, reference is made to the accompanying drawings and descriptive matter in which a preferred embodiment of the invention is illustrated.